Polyomavirus nephropathy after kidney transplantation

Description

A 68-year-old woman was transplanted pre-emptively with a kidney from a deceased donor in May 2012. Her immunosuppressive treatment included thymoglobulin, and tacrolimus, mycophenolate mofetyl (MMF), methylprednisolone. Ten months later, a positive urinalysis for decoy cells (figure 1) preceded a rise in creatinine to 2 mg/dL. Blood PCR for BK DNA detected 45 915 copies/mL. Kidney biopsy disclosed BK virus nephropathy (BKVN; figure 2). MMF was withdrawn and tacrolimus decreased to 4 ng/mL trough level. Three months later, the virus was undetectable. Creatinine remained stable over the following years (2 mg/dL). Donor-specific anti-HLA antibodies remained negative.

Figure 1

Urine cytology shows decoy cells corresponding to tubular epithelial cells infected with BK virus and shed in the urine. (A) Some epithelial cells have enlarged nuclei with ground glass appearance (arrows). (B) Immunohistochemistry staining using antibody against simian virus 40 large T antigen revealing infected cells.

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